Fixes #11: orocos_kdl now has cmake rules oroco-kdl

update cmake to use orocos_kdl as plain cmake package instead of catkin package

Signed-off-by: Ruben Smits <ruben.smits@intermodalics.eu>
Merge pull request #12 from smits/hydro-devel

Fixes #11: orocos_kdl now has cmake rules oroco-kdl